Mechanism and prevention of rockburst in deep asymmetric goaf areas coal seam main roadway

ObjectiveWith an increase in the utilization of main roadways in coal seams, rockburst have occurred increasingly more frequently in these main roadways. Investigating the mechanisms behind these rockburst under specific conditions, as well as differentiated prevention and control measures, holds great significance for the safe extraction of deep coal resources.Methods This study investigated the main roadways at risk of strong rockburst within a coal mine in Inner Mongolia. By integrating a range of methods, including field measurement, theoretical analysis, and FLAC3D-based numerical simulation, this study examined the evolutionary patterns of both the surrounding rock stress and the overburden structure in the main roadways during the formation of the asymmetric goaf structure on both sides of the main roadways. An indicator was developed to discriminate the rockburst risk in main roadways, and the mechanisms underlying the rockburst-induced instability of the main roadways were revealed. Finally, this study proposed the philosophy for targeted prevention and control of the rockburst. Results and Conclusions The results indicate that the goaf area and the evolution of the overburden structure represent primary factors influencing the rockburst risk in the main roadway area, while the formation of an asymmetric goaf structure further increases the risk. During the evolution of the asymmetric goaf structure, the vertical stress progressively evolved into the maximum principal stress, exhibiting a bimodal distribution within the coal pillar zone adjacent to the main roadways. With an increase in the goaf area on the west side of the main roadway area, the vertical stress acting on the surrounding rocks of the main roadways continued rising, with the stress increment first increasing and then decreasing. The main air return roadway consistently fell within the stress peak zone in the west, with a maximum stress of up to 38.7 MPa. The overburden structure above the coal pillar zone evolved from an asymmetric T shape into a symmetric T shape, intensifying the mutual feedback of the rock layer activity on both sides of the roadways. Influenced by changes in the goaf structure on both sides of the main roadways, the surrounding rocks of the main roadways experienced stress concentration and increased damage. As the localized stress of the surrounding rocks exceeded their critical failure load, the surrounding rocks were displaced instantaneously toward the interior of the roadways, triggering rockburst. The critical failure loads of rockburst in roadway roofs and floors were determined at 32.8 MPa and 24.7 MPa, respectively. Zones with a potential rockburst risk gradually expanded with the evolution of the asymmetric goaf structure. A collaborative prevention and control scheme integrating load reduction, pressure relief, and support at regional and local scales was developed, focusing on measures such as the location optimization of the main air return roadway and deep hole blasting for roof cutting. Field validation demonstrates that this scheme can effectively reduce the rockburst risk. Overall, the results of this study can provide a valuable reference for the prevention and control of rockburst in main roadways in coal seams under similar mining conditions.